Liquid crystal display panel and manufacturing method thereof

ABSTRACT

A liquid crystal display panel, a pixel electrode in each of the pixels includes a first linear electrode group extending parallel to an azimuth of approximately 45°, a second linear electrode group extending parallel to an azimuth of approximately 135°, a third linear electrode group extending parallel to an azimuth of approximately 225°, and a fourth linear electrode group extending parallel to an azimuth of approximately 315°. One of the first alignment film and the second alignment film includes a first alignment region provided with a pre-tilt angle at an azimuth of approximately 225°, a third alignment region provided with a pre-tilt angle at an azimuth of approximately 45°, and a region provided with substantially no pre-tilt angle or a pre-tilt angle at an azimuth approximately perpendicular to the linear electrode group on which the region is superimposed. The other of the first alignment film and the second alignment film includes a second alignment region provided with a pre-tilt angle at an azimuth of approximately 135°, a fourth alignment region provided with a pre-tilt angle at an azimuth of approximately 315°, and a region provided with substantially no pre-tilt angle or a pre-tilt angle at an azimuth approximately perpendicular to the linear electrode group on which the region is superimposed.

TECHNICAL FIELD

The present invention relates to liquid crystal display panels andmanufacturing methods thereof. More specifically, the present inventionrelates to a liquid crystal display panel that exhibits a hightransmittance and enhanced response characteristics, can sufficientlyremove a mark left by pushing with a finger, and is easilymanufacturable; and a manufacturing method thereof.

BACKGROUND ART

Liquid crystal display panels have a configuration in which a liquidcrystal display element is held between paired glass substrates, forexample, and have characteristics such as thin profile, light weight,and low power consumption. Having such characteristics, liquid crystaldisplay panels are indispensable for products used in daily life andbusiness, such as automotive navigation systems, electronic bookreaders, digital photo frames, industrial equipment, televisions,personal computers, smartphones, and tablet PCs. For these applications,liquid crystal display panels in various modes have been developed whichemploy electrode arrangements and substrate designs to vary the opticalcharacteristics of liquid crystal layers.

Recent display modes for liquid crystal display panels include verticalalignment (VA) modes which align liquid crystal molecules havingnegative anisotropy of dielectric constant in the directionperpendicular to the substrate surfaces. Vertical alignment mode liquidcrystal display panels are used in the applications described aboveowing to their wide viewing angle. In particular, the following liquidcrystal display panels have been put into practical use: multi-domainvertical alignment (MVA) liquid crystal display panels in which one ofthe substrates is provided with electrode slits and the other isprovided with projections, as alignment control structures, for pixeldivision (alignment division); and patterned vertical alignment (PVA)mode liquid crystal display panels in which both of the substrates areprovided with electrode slits for pixel division (alignment division).

The MVA mode and the PVA mode, however, can still be improved in thattheir response speed is low. In other words, upon application ofhigh-level voltage to switch the mode from black to white, only liquidcrystal molecules near the electrode slits and projections reactinstantly and liquid crystal molecules away from these alignment controlstructures are slow to respond.

In order to increase the response speed, it is effective to provide analignment film to the entire surface of each substrate, performalignment treatment on the films, and provide a pre-tilt angle to liquidcrystal molecules in advance. Also in the VA mode, by slightly tiltingliquid crystal molecules in advance from the vertical alignment films,liquid crystal molecules can be easily tilted when voltage is applied tothe liquid crystal layer, and thus the response speed can be increased.

Examples of a VA mode liquid crystal display device utilizing verticalalignment films whose alignment treatment directions on the substratesare perpendicular to each other to give a twist structure to liquidcrystal molecules include a liquid crystal display device disclosed inPatent Literature 1. The liquid crystal display device includes avertical alignment liquid crystal layer; a first substrate and a secondsubstrate; a first electrode, which is arranged on the first substrateso as to face the liquid crystal layer; a second electrode, which isarranged on the second substrate so as to face the liquid crystal layer;and at least one alignment film, which is arranged in contact with theliquid crystal layer, wherein either the first substrate or the secondsubstrate includes an opaque member, which includes an opaque portionfor shielding an intersection between a boundary area of each of thefirst, second, third and fourth liquid crystal domains, which isadjacent to another one of the liquid crystal domains, and one of thefirst, second, third and fourth edge portions from incoming light.

Examples of a VA mode liquid crystal display device having afour-division alignment structure in which a pre-tilt angle is providedto liquid crystal molecules in advance include a liquid crystal displaydevice disclosed in Patent Literature 2. The liquid crystal displaydevice includes two polarizing plates whose polarization axes areperpendicular to each other; and multiple pixels. In the display device,the pixels each include a liquid crystal layer containing a nematicliquid crystal material whose anisotropy of dielectric constant isnegative, a first electrode, a second electrode facing the firstelectrode across the liquid crystal layer, and paired vertical alignmentfilms disposed between the first electrode and the liquid crystal layerand between the second electrode and the liquid crystal layer. The firstelectrode includes a main portion and multiple branch portions coupledwith the main portion. The branch portions include a first group withmultiple first branches extending in the first azimuth direction instripes, a second group with multiple second branches extending in thesecond azimuth direction in stripes, a third group with multiple thirdbranches extending in the third azimuth direction in stripes, and afourth group with multiple fourth branches extending in the fourthazimuth direction in stripes. A difference between any two of the firstazimuth, second azimuth, third azimuth, and fourth azimuth isapproximately equal to an integer multiple of 90°, and the azimuths forman angle of approximately 45° with the polarization axes of the twopolarizing plates. When no voltage is applied to the liquid crystallayer, the pre-tilt azimuths of liquid crystal molecules near the pairedrespective vertical alignment films are defined by the paired verticalalignment films.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 5184618 B-   Patent Literature 2: JP 2011-85738 A

SUMMARY OF INVENTION Technical Problem

However, the liquid crystal display panel disclosed in Patent Literature1 (such a liquid crystal display panel is also referred to as afour-domain-reverse twisted nematic (4D-RTN) alignment liquid crystaldisplay panel because the alignment region in a pixel is divided intofour and the alignment treatment directions on the substrates areperpendicular to each other) has the following problems (1) and (2)caused by increase in definition of pixels in recent liquid crystaldisplay panels.

(1) The proportion of irregular alignment regions in a pixel hasincreased, and thus the alignment needs to be more stabilized (forexample, see FIG. 51). (2) In the 4D-RTN alignment liquid crystaldisplay panel disclosed in Patent Literature 1, fylfot dark lines aregenerated and thus the transmittance and response performance need to beenhanced.

These problems (1) and (2) are presumed to be due to the followingfactors [1] and [2].

[1] The twist angle is greater than 90° between the alignment directionof liquid crystal molecules LC1 affected by an oblique electric fieldgenerated in the pixel edge portion shown in FIG. 52 (liquid crystalmolecules on the outline of the quadrangular pixel) and the alignmentdirection of liquid crystal molecules LC2 surrounded by a dot-dashedline in a domain in which liquid crystal molecules are stably aligned.This produces irregular alignment regions (dark line edge portions)surrounded by dashed lines, leading to alignment disorder. Furthermore,reduction in pixel size causes the width of an irregular alignmentregion to be about 10 μm, which increases the proportion of irregularalignment regions and may eventually destabilize the alignment in theentire pixel. [2] The width of irregular alignment regions and the otherdark line main portions shown in FIG. 52 is about 10 μm. With thisstructure, reduction in pixel size decreases the proportion of regionsother than the dark lines, possibly decreasing the transmittance andresponse performance.

Patent Literature 2 also discloses in FIG. 6 and FIG. 7 an alignmenttreatment method of the embodiment of Patent Literature 2. Thisalignment treatment method, however, fails to produce a liquid crystaldisplay device with reduced fylfot dark lines.

FIG. 72 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a thin-filmtransistor (TFT) substrate, together with exposure directions andscanning directions, in each pixel in the liquid crystal display deviceshown in FIG. 6 of Patent Literature 2. FIG. 73 is a conceptual viewshowing pre-tilt directions of liquid crystal molecules provided byfirst exposure, second exposure, and both of the exposure treatments ofa photo-alignment film of a color filter (CF) substrate, together withexposure directions and scanning directions, in each pixel in the liquidcrystal display device shown in FIG. 7 of Patent Literature 2. FIG. 74is a conceptual view showing liquid crystal layer alignment achieved bythe photo-alignment film of the TFT substrate in FIG. 72 and thephoto-alignment film of the CF substrate in FIG. 73 in combination.

Since the exposure direction and the scanning direction are parallel toeach other in the alignment treatment method shown in FIG. 72 and FIG.73, a conventional exposure device can be used. The liquid crystal layeralignment achieved by this alignment method, however, is not radialalignment with reduced fylfot dark lines (for example, the alignmentdirection of liquid crystal molecules shown in FIG. 12(b) of PatentLiterature 2), as shown in FIG. 74.

FIG. 7 of Patent Literature 2 is a view showing the exposure directionand the scanning direction for the CF substrate from the alignment filmsurface of the photo-alignment film (view with the photo-alignment filmsurface facing up). Meanwhile, FIG. 72 and FIG. 73 each show theexposure direction and the scanning direction viewed from the topsurface (surface facing the viewer) of the liquid crystal display panelincluding the TFT substrate and the CF substrate bonded to each other asin the other drawings of the present invention. FIG. 72 is a view withthe alignment film surface of the photo-alignment film on the TFTsubstrate facing up. FIG. 73 is a view with the alignment film surfaceof the photo-alignment film on the CF substrate facing down.

Moreover, although FIG. 12(b) of Patent Literature 2 discloses a 4D-RTNalignment liquid crystal display panel providing radial alignment as aconventional technology, such a 4D-RTN alignment liquid crystal displaypanel has the following problems (3) and (4).

(3) Electrodes provided with slits (slit electrodes) as shown in FIG.1(a) of Patent Literature 2 can be used to reduce the width of across-shaped dark line generated in the center portion of a pixel. Thisconfiguration, however, may inhibit removal of a mark left by pushingwith a finger, and thus needs to be improved so as to be able to removea mark left by pushing with a finger. (4) The 4D-RTN alignment liquidcrystal display panel shown in FIG. 12(b) of Patent Literature 2 as aconventional technology can reduce fylfot dark lines. However, such adisplay panel is difficult to produce with a conventionalphoto-alignment exposure device (apparatus for manufacturing a liquidcrystal panel) and thus the display panel requires development of a newexposure device. Moreover, such an exposure device is difficult toproduce because of problems such as the size larger than that ofconventional exposure devices, thereby increasing the production cost.

The problems (3) and (4) described above are presumed to be due to thefollowing factors [3] and [4].

[3] The direction in which liquid crystal molecules are rotated foralignment by electric fields generated by a slit electrode is differentfrom the pre-tilt direction of the liquid crystal molecules provided byphoto-alignment. [4] Since the direction (exposure direction) in whichliquid crystal molecules are desired to be aligned (pre-tilted) isperpendicular to the scanning direction (moving direction of thesubstrate) by the exposure device, exposure with a conventional exposuredevice is difficult.

The factor [4] is further described. FIG. 75 is a conceptual viewshowing pre-tilt directions of liquid crystal molecules provided byfirst exposure, second exposure, and both of the exposure treatments ofa photo-alignment film of a TFT substrate, together with exposuredirections and scanning directions, in each pixel in the liquid crystaldisplay device described in paragraph [0040] of Patent Literature 2.FIG. 76 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each pixelin the liquid crystal display device described in paragraph [0040] ofPatent Literature 2. FIG. 77 is a conceptual view showing liquid crystallayer alignment achieved by the photo-alignment film of the TFTsubstrate in FIG. 75 and the photo-alignment film of the CF substrate inFIG. 76 in combination.

Radial alignment reducing fylfot dark lines shown in FIG. 77 can beachieved by the method described in paragraph [0040] of PatentLiterature 2 (see FIG. 75 to FIG. 77), but the exposure direction andthe scanning direction are perpendicular and not parallel to each otheras shown in FIG. 75 and FIG. 76.

Patent Literature 2 itself actually does not mention scanningdirections. Hence, the scanning direction (direction in which scanningcan be performed) is drawn in each of FIG. 72, FIG. 73, FIG. 75, andFIG. 76 on the assumption that the production process involves commonscanning.

The present invention has been made in view of the above current stateof the art and aims to provide a liquid crystal display panel thatexhibits a high transmittance and rapid response, can sufficientlyremove a mark left by pushing with a finger, and is easilymanufacturable; and a manufacturing method thereof.

Solution to Problem

The inventors of the present invention have made various studies on aliquid crystal display panel which can achieve a high transmittance andrapid response while maintaining the simplicity of the alignmenttreatment process for the alignment films. As a result, they havefocused on a four domain-electrically controlled birefringence (4D-ECB)alignment liquid crystal display panel which is birefringent for lightpassing through the liquid crystal display panel. In this liquid crystaldisplay panel, the alignment region in each pixel or half pixel isdivided into four, and photo-alignment films are used which align liquidcrystal molecules in the direction approximately perpendicular to thefilm surfaces with no voltage applied while providing a pre-tilt angleto the liquid crystal molecules in regions subjected to photo-alignmenttreatment. The films align the liquid crystal molecules in the directionmore parallel to the alignment film surfaces with voltage higher thanthe threshold value applied. The inventors have decided to employ a new4D-ECB alignment structure producible with a conventional exposuredevice and employed slit electrodes. They have then found that 4D-ECBalignment in a specific direction can eliminate irregular alignmentregions in the edge portions and the slit electrodes can reduce thewidth of the dark lines in the main portion. This enables stablealignment even in a high-definition liquid crystal display panel with asmall pixel size. As a result, a high transmittance and rapid responsecan be achieved, so that the above problems (1) and (2) can be solved.The inventors have also found that a mark left by pushing with a fingercan be sufficiently removed by setting the pre-tilt direction of theliquid crystal molecules to be at the same azimuth as the direction inwhich liquid crystal molecules are rotated for alignment by electricfields generated by slit electrodes. Furthermore, the inventors havefound that the scanning exposure can be performed with a conventionalexposure device by slight modification of the device and thus the aboveproblems (3) and (4) can be solved. Thereby, the inventors have arrivedat the present invention.

In other words, one aspect of the present invention may be a liquidcrystal display panel including multiple pixels arranged in a matrix,including in the given order: a first polarizing plate; a firstsubstrate including pixel electrodes each provided with a slit; a firstalignment film; a liquid crystal layer containing liquid crystalmolecules having negative anisotropy of dielectric constant; a secondalignment film; a second substrate including a counter electrode; and asecond polarizing plate, the first polarizing plate and the secondpolarizing plate being arranged such that their polarization axes areperpendicular to each other, with an azimuth in a transverse directionof each pixel defined as 0°, the pixel electrode in each of the pixelsincluding a first linear electrode group extending parallel to anazimuth of approximately 45°, a second linear electrode group extendingparallel to an azimuth of approximately 135°, a third linear electrodegroup extending parallel to an azimuth of approximately 225°, and afourth linear electrode group extending parallel to an azimuth ofapproximately 315°, the first alignment film and the second alignmentfilm each aligning the liquid crystal molecules in a directionapproximately perpendicular to a film surface with no voltage applied tothe liquid crystal layer while providing a pre-tilt angle to the liquidcrystal molecules in at least one region, one of the first alignmentfilm and the second alignment film including a first alignment regionsuperimposed on the first linear electrode group in a plan view andprovided with a pre-tilt angle at an azimuth of approximately 225°, athird alignment region superimposed on the third linear electrode groupin a plan view and provided with a pre-tilt angle at an azimuth ofapproximately 45°, and a region superimposed on the second or fourthlinear electrode group in a plan view and provided with substantially nopre-tilt angle or a pre-tilt angle at an azimuth approximatelyperpendicular to the linear electrode group on which the region issuperimposed, the other of the first alignment film and the secondalignment film including a second alignment region superimposed on thesecond linear electrode group in a plan view and provided with apre-tilt angle at an azimuth of approximately 135°, a fourth alignmentregion superimposed on the fourth linear electrode group in a plan viewand provided with a pre-tilt angle at an azimuth of approximately 315°,and a region superimposed on the first or third linear electrode groupin a plan view and provided with substantially no pre-tilt angle or apre-tilt angle at an azimuth approximately perpendicular to the linearelectrode group on which the region is superimposed. The pre-tilt anglemeans a tilt angle provided in advance to liquid crystal molecules nearthe substrates with no voltage applied, such that the liquid crystalmolecules in the liquid crystal layer are tilted at a desired azimuthwhen voltage higher than the threshold voltage is applied. The liquidcrystal molecules near the alignment films in regions provided with apre-tilt angle are aligned in the direction substantially perpendicularto the alignment films and at a tilt when no voltage is applied to theliquid crystal layer. Upon application of voltage to the liquid crystallayer, the liquid crystal molecules are further significantly tilted atthe tilt azimuth.

Another aspect of the present invention may be a method formanufacturing the liquid crystal display panel of the present invention,including a photo-alignment treatment step of irradiating a firstsubstrate provided with a first alignment film on a surface and a secondsubstrate provided with a second alignment film on a surface with lightemitted by a light source through a polarizer, wherein thephoto-alignment treatment step is performed while the first substrate orthe second substrate is moved or the light source is moved relative tothe first substrate or the second substrate, the light irradiationdirection for the first substrate or the second substrate is parallel tothe moving direction of the first substrate or the second substrate orthe moving direction of the light source, and a polarization axis of thepolarizer and the light irradiation direction are different from eachother. The difference here is preferably 10° or greater, more preferably15° or greater, still more preferably 30° or greater. The polarizationaxis of the polarizer and the light irradiation direction particularlypreferably form an angle of approximately 45°. Furthermore, apolarization axis of the polarizer projected on a surface of the firstsubstrate or a surface of the second substrate and the light irradiationdirection may form an angle of approximately 45°. The present inventionis described in detail below.

The expression “approximately 45°” means any value falling within therange of 45°±15°, preferably 45°. The expression “approximately 135°”means any value falling within the range of 135°±15°, preferably 135°.The expression “approximately 225°” means any value falling within therange of 225°±150, preferably 225°. The expression “approximately 315°”means any value falling within the range of 315°±15°, preferably 315°.The “plan view” means a view from the top (surface facing the viewer) ofa liquid crystal panel including the first substrate and the secondsubstrate bonded to each other.

In the liquid crystal display panel of the present invention, the liquidcrystal layer contains liquid crystal molecules having negativeanisotropy of dielectric constant and each of the first alignment filmand the second alignment film aligns the liquid crystal molecules in thedirection approximately perpendicular to the film surface with novoltage applied to the liquid crystal layer while providing a pre-tiltangle to the liquid crystal molecules in a region subjected tophoto-alignment treatment. Such a liquid crystal layer and alignmentfilms enable production of a 4D-ECB alignment liquid crystal displaypanel which aligns liquid crystal molecules in the directionapproximately perpendicular to the substrate surfaces and provideshybrid alignment or twist alignment between the substrates.

In the liquid crystal display panel of the present invention, each pixelelectrode preferably includes a cross-shaped electrode portionsuperimposed on boundaries between the first alignment region, thesecond alignment region, the third alignment region, and the fourthalignment region in a plan view, and the first linear electrode group,the second linear electrode group, the third linear electrode group, andthe fourth linear electrode group which extend from the cross-shapedelectrode portion. The boundaries between the first alignment region,the second alignment region, the third alignment region, and the fourthalignment region are the boundary between the first alignment region andthe second alignment region, the boundary between the second alignmentregion and the third alignment region, the boundary between the thirdalignment region and the fourth alignment region, and the boundarybetween the fourth alignment region and the first alignment region ineach pixel.

In the liquid crystal display panel of the present invention, the firstlinear electrode group, the second linear electrode group, the thirdlinear electrode group, and the fourth linear electrode group arepreferably line-symmetric about at least one of two linear portionsconstituting the cross-shaped electrode portion, more preferably abouteach of the two linear portions constituting the cross-shaped electrodeportion.

In the liquid crystal display panel of the present invention, the firstlinear electrode group, the second linear electrode group, the thirdlinear electrode group, and the fourth linear electrode group arepreferably alternately connected to opposite sides of at least one oftwo linear portions constituting the cross-shaped electrode portion,more preferably from each of the two linear portions constituting thecross-shaped electrode portion.

In the liquid crystal display panel of the present invention, each pixelelectrode preferably includes a quadrangular portion, linear electrodeportions extending from the quadrangular portion to be superimposed onboundaries between the first alignment region, the second alignmentregion, the third alignment region, and the fourth alignment region in aplan view, and the first linear electrode group, the second linearelectrode group, the third linear electrode group, and the fourth linearelectrode group which extend from the quadrangular portion and thelinear electrode portions.

Advantageous Effects of Invention

The liquid crystal display panel of the present invention can exhibit ahigh transmittance and rapid response and sufficiently remove a markleft by pushing with a finger. The method for manufacturing the liquidcrystal display panel of the present invention can easily produce aliquid crystal display panel that can exhibit a high transmittance andrapid response and sufficiently remove a mark left by pushing with afinger.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Embodiment 1.

FIG. 2 is a schematic plan view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substratein each half pixel in the liquid crystal display panel of Embodiment 1.

FIG. 3 is a schematic plan view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substratein each half pixel in the liquid crystal display panel of Embodiment 1.

FIG. 4 is an enlarged detailed view of FIG. 1.

FIG. 5 is a simulation result corresponding to FIG. 4.

FIG. 6 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Embodiment 1.

FIG. 7 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Embodiment 1.

FIG. 8 is a schematic plan view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate and a pre-tilt direction ofliquid crystal molecules near the CF substrate in each half pixel in theliquid crystal display panel of Embodiment 1.

FIG. 9 is a schematic plan view of an electrode provided with slits ineach half pixel in the liquid crystal display panel of Embodiment 1.

FIG. 10 is an enlarged view of a portion surrounded by a dashed line inFIG. 9.

FIG. 11 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a 4D-ECB alignment liquid crystaldisplay panel.

FIG. 12 shows alignment of liquid crystal molecules achieved by thepre-tilt provided by the TFT substrate of the liquid crystal displaypanel shown in FIG. 11.

FIG. 13 shows alignment of liquid crystal molecules achieved by electricfields generated by a slit electrode of the TFT substrate in the liquidcrystal display panel shown in FIG. 11.

FIG. 14 shows alignment of liquid crystal molecules near the TFTsubstrate and in the liquid crystal layer upon pushing with a finger andupon removal of the finger in the liquid crystal display panel shown inFIG. 11.

FIG. 15 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a liquid crystal display panel of afirst modified example of Embodiment 1.

FIG. 16 is a schematic cross-sectional view showing an OFF state in aregion (1) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 17 is a schematic cross-sectional view showing an ON state in theregion (1) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 18 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 19 is a schematic cross-sectional view showing an OFF state in aregion (2) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 20 is a schematic cross-sectional view showing an ON state in theregion (2) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 21 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 22 is a schematic cross-sectional view showing an OFF state in aregion (3) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 23 is a schematic cross-sectional view showing an ON state in theregion (3) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 24 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 25 is a schematic cross-sectional view showing an OFF state in aregion (4) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 26 is a schematic cross-sectional view showing an ON state in theregion (4) in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1.

FIG. 27 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a liquid crystal display panel ofReference Example 1.

FIG. 28 is a schematic cross-sectional view showing an OFF state in aregion (1) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 29 is a schematic cross-sectional view showing an ON state in theregion (1) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 30 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 31 is a schematic cross-sectional view showing an OFF state in aregion (2) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 32 is a schematic cross-sectional view showing an ON state in theregion (2) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 33 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 34 is a schematic cross-sectional view showing an OFF state in aregion (3) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 35 is a schematic cross-sectional view showing an ON state in theregion (3) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 36 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 37 is a schematic cross-sectional view showing an OFF state in aregion (4) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 38 is a schematic cross-sectional view showing an ON state in theregion (4) in each half pixel in the liquid crystal display panel ofReference Example 1.

FIG. 39 is a schematic view of an UV exposure device in Embodiment 1.

FIG. 40 includes schematic views showing first exposure in Embodiment 1.

FIG. 41 includes schematic views showing second exposure in Embodiment1.

FIG. 42 is a schematic view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a substrate inthe liquid crystal display panel of Embodiment 1.

FIG. 43 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Embodiment 2.

FIG. 44 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Embodiment 3.

FIG. 45 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, thirdexposure, fourth exposure, and all the exposure treatments of aphoto-alignment film of a TFT substrate, together with exposuredirections and scanning directions, in each half pixel in a liquidcrystal display panel of Embodiment 4.

FIG. 46 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, thirdexposure, fourth exposure, and all the exposure treatments of aphoto-alignment film of a CF substrate, together with exposuredirections and scanning directions, in each half pixel in the liquidcrystal display panel of Embodiment 4.

FIG. 47 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in the liquid crystaldisplay panel of Embodiment 4.

FIG. 48 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and aplanar electrode in each half pixel in a liquid crystal display panel ofComparative Example 1.

FIG. 49 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substratein each half pixel in the liquid crystal display panel of ComparativeExample 1.

FIG. 50 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substratein each half pixel in the liquid crystal display panel of ComparativeExample 1.

FIG. 51 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and aplanar electrode in each half pixel of 82 μm×245 μm pixels included inthe liquid crystal display panel of Comparative Example 1.

FIG. 52 is a simulation result corresponding to FIG. 51.

FIG. 53 is a schematic plan view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate and a pre-tilt direction ofliquid crystal molecules near the CF substrate, in each half pixel inthe liquid crystal display panel of Comparative Example 1.

FIG. 54 is a schematic plan view showing a planar electrode in each halfpixel in the liquid crystal display panel of Comparative Example 1.

FIG. 55 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a 4D-RTN alignment liquid crystaldisplay panel.

FIG. 56 shows alignment of liquid crystal molecules achieved by thepre-tilt provided by the TFT substrate of the liquid crystal displaypanel shown in FIG. 55.

FIG. 57 shows alignment of liquid crystal molecules achieved by electricfields generated by a slit electrode of the TFT substrate in the liquidcrystal display panel shown in FIG. 55.

FIG. 58 shows alignment of liquid crystal molecules near the TFTsubstrate and in the liquid crystal layer upon pushing with a finger andupon removal of the finger in the liquid crystal display panel shown inFIG. 55.

FIG. 59 is a schematic view of an exposure device in Comparative Example1.

FIG. 60 is a schematic view showing first exposure in ComparativeExample 1.

FIG. 61 is a schematic view showing second exposure in ComparativeExample 1.

FIG. 62 is a schematic view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a substrate inthe liquid crystal display panel of Comparative Example 1.

FIG. 63 is a schematic plan view whose left part shows exposure of aphoto-alignment film in the case of parallel exposure direction andscanning direction viewed from directly above the photo-alignment filmand whose right part shows incident angle distribution of light from alight source along the y1-y2 axis in the left part.

FIG. 64 is a perspective view of exposure of a photo-alignment film inthe case of parallel exposure direction and scanning direction.

FIG. 65 is a schematic plan view whose left part shows exposure of aphoto-alignment film in the case of perpendicular exposure direction andscanning direction viewed from directly above the photo-alignment filmand whose right part shows incident angle distribution of light from alight source along the y1-y2 axis in the left part.

FIG. 66 is a perspective view of exposure of a photo-alignment film inthe case of perpendicular exposure direction and scanning direction.

FIG. 67 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Comparative Example 2.

FIG. 68 is a schematic plan view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substratein each half pixel in the liquid crystal display panel of ComparativeExample 2.

FIG. 69 is a schematic plan view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substratein each half pixel in the liquid crystal display panel of ComparativeExample 2.

FIG. 70 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Comparative Example 2.

FIG. 71 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Comparative Example 2.

FIG. 72 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substrate,together with exposure directions and scanning directions, in each pixelin the liquid crystal display device shown in FIG. 6 of PatentLiterature 2.

FIG. 73 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each pixelin the liquid crystal display device shown in FIG. 7 of PatentLiterature 2.

FIG. 74 is a conceptual view showing liquid crystal layer alignmentachieved by the photo-alignment film of the TFT substrate in FIG. 72 andthe photo-alignment film of the CF substrate in FIG. 73 in combination.

FIG. 75 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substrate,together with exposure directions and scanning directions, in each pixelin the liquid crystal display device described in paragraph [0040] ofPatent Literature 2.

FIG. 76 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each pixelin the liquid crystal display device described in paragraph [0040] ofPatent Literature 2.

FIG. 77 is a conceptual view showing liquid crystal layer alignmentachieved by the photo-alignment film of the TFT substrate in FIG. 75 andthe photo-alignment film of the CF substrate in FIG. 76 in combination.

DESCRIPTION OF EMBODIMENTS

The present invention is described in more detail below with referenceto embodiments which, however, are not intended to limit the scope ofthe present invention.

The “azimuth” as used herein means a direction in a plane parallel tothe substrate surfaces without consideration of a tilt angle (polarangle, pre-tilt angle) from the normal direction of the substratesurfaces. For example, if an x-axis and a y-axis perpendicular to thex-axis form an xy plane, the x-axis lies at an azimuth in the transversedirection of a pixel, and if the xy plane is parallel to the substratesurfaces, the azimuth is determined counterclockwise in a positive valuefrom the x-axis direction defined as 0°. The “tilt azimuth” of a liquidcrystal molecule near the first substrate means an azimuth at which theliquid crystal molecule is tilted relative to the first substrate (theazimuth obtained by projecting on the first substrate the liquid crystalmolecule tilted from its end near the first substrate to its end awayfrom the first substrate). The “tilt azimuth” of a liquid crystalmolecule near the center of the liquid crystal layer in the thicknessdirection means an azimuth at which the liquid crystal molecule istilted relative to the first substrate. The “tilt azimuth” of a liquidcrystal molecule near the second substrate means an azimuth at which theliquid crystal molecule is tilted relative to the second substrate (theazimuth obtained by projecting on the second substrate the liquidcrystal molecule tilted from its end near the second substrate to itsend away from the second substrate). For example, the tilt azimuth of aliquid crystal molecule LC directly indicated as “LC” in FIG. 1 near thecenter of the liquid crystal layer in the thickness direction is 225°.The “pre-tilt angle” means an angle formed by an alignment film surfaceand the long-axis direction of a liquid crystal molecule near thealignment film when no voltage is applied to the liquid crystal layer.The “threshold voltage” means a voltage level giving, for example, atransmittance of 5% when the transmittance in the bright state is set to100%. The “pre-tilt angle azimuth (pre-tilt direction)” means a tiltazimuth of a liquid crystal molecule near the first substrate or aliquid crystal molecule near the second substrate when no voltage isapplied to the liquid crystal layer. The “liquid crystal layeralignment” as used herein means a tilt azimuth of a liquid crystalmolecule near the center of the liquid crystal layer in the thicknessdirection.

A “pixel” corresponds to a region including a filter of one color (e.g.,red, green, blue, or yellow). In the embodiments below, a countersubstrate is referred to as a color filter (CF) substrate because itincludes color filters. The color filters, however, may not be includedin the counter substrate but in a thin-film transistor (TFT) substrateincluding TFTs for the respective pixels. One of the first substrate andthe second substrate may be a TFT substrate and the other may be a CFsubstrate.

In the OFF state, the liquid crystal display panels of the embodimentsbelow align the liquid crystal molecules having negative anisotropy ofdielectric constant in the direction approximately perpendicular to thealignment film surfaces while providing a pre-tilt angle to the liquidcrystal molecules in regions subjected to photo-alignment treatment. Inthe ON state, the liquid crystal display panels align the liquid crystalmolecules in the direction more parallel to the alignment film surfacesaccording to the applied voltage (voltage applied by the pixel electrodeand the counter electrode) so that the liquid crystal molecules becomebirefringent for light passing through the liquid crystal display panel.

The liquid crystal display panels of the embodiments below eachbasically include multiple pixels arranged in a matrix, and include, inthe following order, a first polarizing plate, a TFT substrate includingpixel electrodes provided with slits, an alignment film on or adjacentto a surface of the TFT substrate facing liquid crystal layer, a liquidcrystal layer containing liquid crystal molecules having negativeanisotropy of dielectric constant, an alignment film on or adjacent to asurface of a CF substrate facing the liquid crystal layer, the CFsubstrate including a counter electrode, and a second polarizing plate.The first polarizing plate and the second polarizing plate are arrangedsuch that their polarization axes are perpendicular to each other. Thecounter electrode may include alignment control structures such as ribsor slits, but is preferably a planar electrode with no alignment controlstructures.

Embodiment 1

FIG. 1 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Embodiment 1. FIG. 1 shows the above relation in the ONstate (in white display). FIG. 1 also shows dark lines between alignmentregions. FIG. 2 is a schematic plan view showing pre-tilt directions ofliquid crystal molecules provided by first exposure, second exposure,and both of the exposure treatments of a photo-alignment film of a TFTsubstrate in each half pixel in the liquid crystal display panel ofEmbodiment 1. FIG. 3 is a schematic plan view showing pre-tiltdirections of liquid crystal molecules provided by first exposure,second exposure, and both of the exposure treatments of aphoto-alignment film of a CF substrate in each half pixel in the liquidcrystal display panel of Embodiment 1. Here, a pixel in Embodiment 1includes two of the half pixels shown in FIGS. 1 to 3 in the verticaldirection but may include two of the half pixels in the horizontaldirection.

The liquid crystal display panel of Embodiment 1 has the followingfeatures.

(1) The liquid crystal molecules are radially aligned.

(2) With the azimuth in the transverse direction of a pixel defined as0°, a first alignment region (1) and a third alignment region (3) inFIG. 1 (quadrangular regions shown with the signs (1) and (3) in FIG. 1)are provided with a pre-tilt direction at an azimuth of 225° and at anazimuth of 45°, respectively, near the TFT substrate. Also, a secondalignment region (2) and a fourth alignment region (4) in FIG. 1(quadrangular regions shown with the signs (2) and (4) in FIG. 1) areprovided with a pre-tilt direction at an azimuth of 135° and at anazimuth of 315°, respectively, near the CF substrate.

These four alignment regions are arranged in the order of the firstalignment region (1), the second alignment region (2), the thirdalignment region (3), and the fourth alignment region (4) in thecounterclockwise direction in a view from the surface facing the viewer.

(3) With the azimuth in the transverse direction of a pixel defined as0°, the directions in which slits (linear electrode groups) of eachpixel electrode (slit electrode) in the TFT substrate in the firstalignment region (1), the second alignment region (2), the thirdalignment region (3), and the fourth alignment region (4) shown in FIG.1 are at an azimuth of 45°, an azimuth of 135°, an azimuth of 225°, andan azimuth of 315°, respectively. The direction in which each linearelectrode group extends is parallel to the pre-tilt direction in thecorresponding alignment region. Also, the direction in which liquidcrystal molecules are rotated for alignment by electric fields generatedby the slit electrode is the same as the pre-tilt direction(s) providedby the photo-alignment film(s) on or adjacent to the TFT substrateand/or the CF substrate.

The pre-tilt angle of liquid crystal molecules is preferably, forexample, 85° to 89.5°. The pre-tilt angle is more preferably 88.5° orgreater.

The “radial” alignment as used herein means that the liquid crystalmolecules near the center of the liquid crystal layer in the thicknessdirection are aligned at an azimuth of approximately 225°, an azimuth ofapproximately 315°, an azimuth of approximately 45°, and an azimuth ofapproximately 135° in the first alignment region (1), the secondalignment region (2), the third alignment region (3), and the fourthalignment region (4) shown in FIG. 1, respectively.

FIG. 4 is an enlarged detailed view of FIG. 1. FIG. 5 is a simulationresult corresponding to FIG. 4.

The liquid crystal display panel of Embodiment 1 includes radiallyaligned liquid crystal molecules. With this configuration, as shown inFIG. 5, the twist angle formed by the long-axis directions of liquidcrystal molecules affected by oblique electric fields generated in theedge portion of the slit electrode (liquid crystal molecules LC1 on theoutline of the quadrangular half pixel) and the long-axis directions ofliquid crystal molecules LC2 in the domain is smaller than 90°, so thatthe irregular alignment regions can be eliminated from the portionssurrounded by dashed lines in FIG. 5, as compared with thelater-described liquid crystal display panel of Comparative Example 1.Thereby, the alignment regions in the domains are expanded and thusstable alignment is achieved.

The liquid crystal display panel of Embodiment 1 includes electrodesprovided with radial slits. Such electrodes can reduce the width of darklines at the center (for example, as shown in FIG. 4, the widths of d1and d2 are each reduced to narrower than 10 μm) and expand the alignmentregions in the domains.

The liquid crystal display panel of Embodiment 1 has an increasedtransmittance owing to reduced dark line regions. The liquid crystaldisplay panel also exhibits enhanced response performance owing tostable alignment.

The liquid crystal display panel of Embodiment 1 has a structure inwhich the pre-tilt directions of liquid crystal molecules near the TFTsubstrate and liquid crystal molecules near the CF substrate are at thesame azimuth as the direction in which the liquid crystal molecules arerotated for alignment by electric fields generated by the slitelectrode. Thereby, the liquid crystal display panel can sufficientlyremove a mark left by pushing with a finger and exhibit improved displayquality as compared with the later-described liquid crystal displaypanel of Comparative Example 2.

FIG. 6 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Embodiment 1. FIG. 7 is aconceptual view showing pre-tilt directions of liquid crystal moleculesprovided by first exposure, second exposure, and both of the exposuretreatments of a photo-alignment film of a CF substrate, together withexposure directions and scanning directions, in each half pixel in theliquid crystal display panel of Embodiment 1.

In manufacture of the liquid crystal display panel of Embodiment 1, asdescribed below, the polarization axis of the exposure device is rotatedby 45° such that the exposure direction for the photo-alignment film ofthe substrate and the scanning direction (moving direction of thesubstrate) are parallel to each other. In this manner, performingscanning exposure using a simply modified conventional exposure deviceenables manufacture of the liquid crystal display panel of Embodiment 1.Thereby, the liquid crystal display panel of Embodiment 1 can be easilymanufactured.

FIG. 8 is a schematic plan view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate and a pre-tilt direction ofliquid crystal molecules near the CF substrate in each half pixel in theliquid crystal display panel of Embodiment 1.

The liquid crystal display panel of Embodiment 1 achieves afour-division alignment structure as shown in FIG. 8 only by ultravioletlight (UV) exposure as shown in FIG. 6 and FIG. 7.

In the liquid crystal display panel of Embodiment 1, only one of thealignment film of the TFT substrate and the alignment film of the CFsubstrate provides a pre-tilt angle in each of two regions (firstalignment region (1) and second alignment region (2)) of the firstalignment region (1), the second alignment region (2), the thirdalignment region (3), and the fourth alignment region (4) (fourquadrangular regions shown with the signs (1), (2), (3), and (4) in FIG.8), and the alignment film of the TFT substrate and the alignment filmof the CF substrate provide different pre-tilt angles at azimuthsperpendicular to each other in each of the other two regions (thirdalignment region (3) and fourth alignment region (4)) of the fourregions. These configurations are summarized in the following Table 1.The exposure states corresponding to the “large”, “small”, and “none”under “pre-tilt” in the following Table 1 are shown in the followingTable 2. The “hybrid alignment” alignment region means an alignmentregion in which liquid crystal molecules near the alignment films of thepaired substrates are aligned in the direction approximatelyperpendicular to the respective substrates and one of the alignmentfilms is exposed to UV light such that the liquid crystal molecules nearthe exposed alignment film are pre-tilted.

TABLE 1 Pre-tilt Alignment achieved by Region TFT CF pre-tilt (UVexposure effect) (1) Large None Tilt near TFT is dominant (hybridalignment) (2) None Large Tilt near CF is dominant (hybrid alignment)(3) Large Small Tilt near TFT is dominant (slightly twisted alignment)(4) Small Large Tilt near CF is dominant (slightly twisted alignment)

TABLE 2 Pre-tilt Exposure state Large Normal exposure Small Doubleexposure (opposite directions) None No exposure

FIG. 9 is a schematic plan view of an electrode provided with slits ineach half pixel in the liquid crystal display panel of Embodiment 1. Inthe liquid crystal display panel of Embodiment 1, upon generation ofelectric fields by a slit electrode (transverse electric field componentgenerated in the direction perpendicular to the slits in a plan view),liquid crystal molecules are aligned in the direction parallel to theslits when voltage is applied to the liquid crystal layer, whereby thetwist is eliminated.

FIG. 10 is an enlarged view of a portion surrounded by a dashed line inFIG. 9. As shown in FIG. 10, the slit electrode generates transverseelectric field components perpendicular to the direction in which theslits extend. This means that the liquid crystal molecules in the liquidcrystal layer are aligned in the direction parallel to the direction inwhich the slits extend (in the direction perpendicular to the transverseelectric field components).

As described above, the liquid crystal display panel of Embodiment 1utilizes a four-division alignment (pre-tilt) structure achieved by UVexposure with specific exposure directions and polarization axes incombination with the alignment provided by electric fields generated byslit electrodes to achieve the 4D-ECB alignment shown in FIG. 1.

In the liquid crystal display panel of Embodiment 1, the alignment filmof the TFT substrate and the alignment film of the CF substrate arephoto-alignment films having a bonded structure of photosensitivegroups. The “photo-alignment film” as used herein means a film formed ofa material whose alignment controlling force changes when irradiatedwith light. A “photo-alignment film having a bonded structure ofphotosensitive groups” means a photo-alignment film having a structurein which photosensitive functional groups contained in the constituentmolecules are bonded to each other. The liquid crystal display panel ofthe present invention may employ an alignment film formed of an organicmaterial, an alignment film formed of an inorganic material, or analignment film obtained by alignment treatment such as rubbing, forexample, instead of the photo-alignment film. Also with such alignmentfilms, the liquid crystal display panel can achieve the effect of thepresent invention.

In the present invention, the alignment film of the TFT substrate andthe alignment film of the CF substrate each preferably have a bondedstructure of at least one photo-sensitive group selected from the groupconsisting of 4-chalcone, 4′-chalcone, coumarin, and cinnamoyl (alsoreferred to as cinnamate) groups.

The photosensitive groups are dimerized or crosslinked when irradiatedwith light and thereby effectively minimize pre-tilt angle variation. Asa result, a liquid crystal display panel having a stable transmittancecan be produced.

In the present invention, the alignment film of the TFT substrate andthe alignment film of the CF substrate each include three alignmentregions provided with different pre-tilt azimuths and a region providedwith substantially no pre-tilt in each half pixel or each pixel. As aresult, in the case of dividing each half pixel or pixel into fourdomains, the alignment treatment step for alignment division is requiredonly twice for each of the first alignment film and the second alignmentfilm, i.e., a total of four times.

(Mark Left by Pushing with Finger in 4D-ECB Alignment Liquid CrystalDisplay Panel)

FIG. 11 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a 4D-ECB alignment liquid crystaldisplay panel. The liquid crystal display panel shown in FIG. 11 issimilar to that in Embodiment 1, except that the pre-tilt direction ofthe liquid crystal molecules is changed as shown in FIG. 11. This liquidcrystal display panel corresponds to a first modified example ofEmbodiment 1. FIG. 12 shows alignment of liquid crystal moleculesachieved by the pre-tilt provided by the TFT substrate of the liquidcrystal display panel shown in FIG. 11. FIG. 13 shows alignment ofliquid crystal molecules achieved by electric fields generated by a slitelectrode of the TFT substrate in the liquid crystal display panel shownin FIG. 11. FIG. 12 and FIG. 13 are enlarged views of the portionsurrounded by a dashed line in FIG. 11, showing the alignment of theliquid crystal molecules near the slit electrode and the TFT substrate.

The alignment of the liquid crystal molecules near the TFT substrateincluding slit electrodes is set depending on the balance between (1)alignment achieved by the pre-tilt and (2) alignment achieved byelectric fields generated by the slit electrodes. In the normal state(when the finger is removed), the alignment (1) achieved by the pre-tiltis dominant, whereas upon pushing with a finger, the gap between the TFTsubstrate and the CF substrate becomes narrow and thus the alignment (2)achieved by electric fields generated by the slit electrode is dominant.

FIG. 14 shows alignment of liquid crystal molecules near the TFTsubstrate and in the liquid crystal layer upon pushing with a finger andupon removal of the finger in the liquid crystal display panel shown inFIG. 11. In FIG. 14, the “provided” state for the “slit” means that theliquid crystal display panel includes the slit electrode shown in FIG.11. The “not provided” state for the “slit” means that a liquid crystaldisplay panel includes no slit electrode but includes a planar electrode(a liquid crystal display panel different from the liquid crystaldisplay panel shown in FIG. 11 only in terms of including a planarelectrode instead of the slit electrode). The “alignment near TFTsubstrate” means the alignment of liquid crystal molecules near the TFTsubstrate in the liquid crystal layer. The “liquid crystal layeralignment” means the alignment of liquid crystal molecules in the liquidcrystal layer or the alignment of liquid crystal molecules in the centerportion, which is other than the portion near the TFT substrate and theportion near the CF substrate, in the liquid crystal layer. The “liquidcrystal layer/TFT alignment (matched)” means that the alignment ofliquid crystal molecules in the center portion of the liquid crystallayer matches (is the same as) the alignment of liquid crystal moleculesnear the TFT substrate in the liquid crystal layer, and shows thealignments. In the 4D-ECB alignment liquid crystal display panelincluding the slit electrode shown in FIG. 11, liquid crystal moleculesin the portion indicated by the letter “A”, liquid crystal molecules inthe portion indicated by the letter “B”, and liquid crystal molecules inthe portion indicated by the letter “C” are all shifted from Alignment ato Alignment b without stopping when the states shift from pushing witha finger to removal of the finger. This configuration is presumed toavoid a mark left by pushing with a finger. In the liquid crystaldisplay panel including a planar electrode instead of a slit electrode,the alignment in any of the portions does not change between pushingwith a finger and removal of the finger, and thus no mark is left bypushing with a finger.

(Cross-Sectional View of 4D-ECB Alignment Liquid Crystal Display Panel)

Cross-sectional views of the liquid crystal display panel of the firstmodified example of Embodiment 1 are described.

FIG. 15 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a liquid crystal display panel of thefirst modified example of Embodiment 1. FIG. 16 is a schematiccross-sectional view showing an OFF state in the first alignment region(1) in each half pixel in the liquid crystal display panel of the firstmodified example of Embodiment 1. FIG. 17 is a schematic cross-sectionalview showing an ON state in the first alignment region (1) in each halfpixel in the liquid crystal display panel of the first modified exampleof Embodiment 1.

In FIG. 16 and FIG. 17, a polarization axis 111 a of a first polarizingplate 111 is at the azimuth of the x-axis and a polarization axis 121 aof a second polarizing plate 121 is at the azimuth of the y-axis. In thedisplay region of the TFT substrate, indium tin oxide (ITO) 115 ispartially provided and a photo-alignment film 117 is entirely providedto a substrate 113 including TFTs. In the display region of the CFsubstrate, ITO 125 and a photo-alignment film 127 are entirely providedto a substrate 123 (to the surface facing the liquid crystal layer)including CFs. The ITO may be replaced by another transparent electrodematerial such as indium zinc oxide (IZO). The same applies to FIG. 19,FIG. 20, FIG. 22, FIG. 23, FIG. 25, and FIG. 26 described below.

The liquid crystal molecules in the first alignment region (1) arepre-tilted near the CF substrate but are not pre-tilted near the TFTsubstrate due to no exposure.

FIG. 18 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1. FIG. 19 is a schematiccross-sectional view showing an OFF state in the second alignment region(2) in each half pixel in the liquid crystal display panel of the firstmodified example of Embodiment 1. FIG. 20 is a schematic cross-sectionalview showing an ON state in the second alignment region (2) in each halfpixel in the liquid crystal display panel of the first modified exampleof Embodiment 1.

The liquid crystal molecules in the second alignment region (2) arepre-tilted near the TFT substrate and are not pre-tilted near the CFsubstrate due to no exposure.

FIG. 21 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1. FIG. 22 is a schematiccross-sectional view showing an OFF state in the third alignment region(3) in each half pixel in the liquid crystal display panel of the firstmodified example of Embodiment 1. FIG. 23 is a schematic cross-sectionalview showing an ON state in the third alignment region (3) in each halfpixel in the liquid crystal display panel of the first modified exampleof Embodiment 1.

The liquid crystal molecules in the third alignment region (3) arepre-tilted near the CF substrate and are less pre-tilted near the TFTsubstrate than near the CF substrate due to double exposure. The slitelectrode further reduces the influence of the pre-tilt provided by theTFT substrate, causing slightly twisted alignment overall. The twistoccurs in the portion surrounded by the dashed line near the TFTsubstrate in FIG. 23.

The electric fields generated by the slit electrodes can reduce theinfluence of the pre-tilt alignment near the TFT substrate.

FIG. 24 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel of thefirst modified example of Embodiment 1. FIG. 25 is a schematiccross-sectional view showing an OFF state in the fourth alignment region(4) in each half pixel in the liquid crystal display panel of the firstmodified example of Embodiment 1. FIG. 26 is a schematic cross-sectionalview showing an ON state in the fourth alignment region (4) in each halfpixel in the liquid crystal display panel of the first modified exampleof Embodiment 1.

The liquid crystal molecules in the fourth alignment region (4) arepre-tilted near the TFT substrate and are less pre-tilted near the CFsubstrate than near the TFT substrate due to double exposure. The slitelectrode further reduces the influence of the pre-tilt provided by theCF substrate, causing slightly twisted alignment overall. The twistoccurs in the portion surrounded by the dashed line near the CFsubstrate in FIG. 26.

The electric fields generated by the slit electrodes can reduce theinfluence of the pre-tilt alignment near the CF substrate.

Reference Example 1

Reference Example 1 is similar to the first modified example ofEmbodiment 1, except that a planar electrode is used instead of a slitelectrode as the electrode of the TFT substrate.

FIG. 27 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a liquid crystal display panel ofReference Example 1. FIG. 28 is a schematic cross-sectional view showingan OFF state in the first alignment region (1) in each half pixel in theliquid crystal display panel of Reference Example 1. FIG. 29 is aschematic cross-sectional view showing an ON state in the firstalignment region (1) in each half pixel in the liquid crystal displaypanel of Reference Example 1.

In FIG. 28 and FIG. 29, a polarization axis 211 a of a first polarizingplate 211 is at the azimuth of the x-axis and a polarization axis 221 aof a second polarizing plate 221 is at the azimuth of the y-axis. In thedisplay region of the TFT substrate, ITO 215 and a photo-alignment film217 are entirely provided to a substrate 213 including TFTs. In thedisplay region of the CF substrate, ITO 225 and a photo-alignment film227 are entirely provided to a substrate 223 (to the surface facing theliquid crystal) including CFs. The ITO may be replaced by anothertransparent electrode material such as indium zinc oxide (IZO). The sameapplies to FIG. 31, FIG. 32, FIG. 34, FIG. 35, FIG. 37, and FIG. 38described below.

The liquid crystal molecules in the first alignment region (1) arepre-tilted near the CF substrate but are not pre-tilted near the TFTsubstrate due to no exposure.

FIG. 30 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel ofReference Example 1. FIG. 31 is a schematic cross-sectional view showingan OFF state in the second alignment region (2) in each half pixel inthe liquid crystal display panel of Reference Example 1. FIG. 32 is aschematic cross-sectional view showing an ON state in the secondalignment region (2) in each half pixel in the liquid crystal displaypanel of Reference Example 1.

The liquid crystal molecules in the second alignment region (2) arepre-tilted near the TFT substrate and are not pre-tilted near the CFsubstrate due to no exposure.

FIG. 33 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel ofReference Example 1. FIG. 34 is a schematic cross-sectional view showingan OFF state in the third alignment region (3) in each half pixel in theliquid crystal display panel of Reference Example 1. FIG. 35 is aschematic cross-sectional view showing an ON state in the thirdalignment region (3) in each half pixel in the liquid crystal displaypanel of Reference Example 1.

The liquid crystal molecules in the third alignment region (3) arepre-tilted near the CF substrate and are less pre-tilted near the TFTsubstrate than near the CF substrate due to double exposure, causingslightly twisted alignment overall. The twist occurs over the range fromthe portion surrounded by the dashed line near the TFT substrate to theportion near the center of the liquid crystal layer in the thicknessdirection in FIG. 35.

FIG. 36 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in the liquid crystal display panel ofReference Example 1. FIG. 37 is a schematic cross-sectional view showingan OFF state in the fourth alignment region (4) in each half pixel inthe liquid crystal display panel of Reference Example 1. FIG. 38 is aschematic cross-sectional view showing an ON state in the fourthalignment region (4) in each half pixel in the liquid crystal displaypanel of Reference Example 1.

The liquid crystal molecules in the fourth alignment region (4) arepre-tilted near the TFT substrate and are less pre-tilted near the CFsubstrate due to double exposure, causing slightly twisted alignmentoverall. The twist occurs over the range from the portion surrounded bythe dashed line near the CF substrate to the portion near the center ofthe liquid crystal layer in the thickness direction in FIG. 38.

In the liquid crystal display panel of the first modified example ofEmbodiment 1 and the liquid crystal display panel of Reference Example1, only one of the photo-alignment film of the TFT substrate and thephoto-alignment film of the CF substrate provides a pre-tilt angle ineach of two regions (first alignment region (1) and second alignmentregion (2)) of the four regions, and the photo-alignment film of the TFTsubstrate and the photo-alignment film of the CF substrate providedifferent pre-tilt angles at azimuths perpendicular to each other ineach of the other two regions (third alignment region (3) and fourthalignment region (4)) of the four regions. These configurations aresummarized in the following Table 3. The exposure states correspondingto the “large”, “small”, and “none” under “pre-tilt” in the followingTable 3 are the same as those in the above Table 2.

TABLE 3 Pre-tilt Alignment achieved by Region TFT CF pre-tilt (UVexposure effect) (1) None Large Tilt near CF is dominant (hybridalignment) (2) Large None Tilt near TFT is dominant (hybrid alignment)(3) Small Large Tilt near CF is dominant (slightly twisted alignment)(4) Large Small Tilt near TFT is dominant (slightly twisted alignment)

Hereinafter, the method for manufacturing the liquid crystal displaypanel of Embodiment 1 is described.

In Embodiment 1, paired substrates before formation of alignment filmswere prepared by a common method.

The first substrate, which is one of the paired substrates, was producedas a thin-film transistor array substrate in which scanning signal linesand data signal lines were formed to intersect each other in a gridshape on a glass substrate with an insulating film in between andthin-film transistors and pixel electrodes were formed at the respectiveintersections. The first substrate was produced by forming a laminate ofthin films and patterning the films through repetition of the followingsteps: (1) thin-film formation by a technique such as sputtering,plasma-enhanced chemical vapor deposition (PVCD), or vapor deposition;(2) resist application which includes coating such as spin coating orroll coating, followed by baking; (3) exposure by a method such as lensprojection (stepper), mirror projection, or proximity; (4) development;(5) etching such as dry etching or wet etching; and (6) resist removalby a method such as plasma (dry) ashing or wet removal.

The second substrate, which is the other of the paired substrates, wasproduced as a color filter substrate by sequentially forming, on a glasssubstrate, (1) a black matrix, (2) RGB color patterns, (3) a protectivefilm, and (4) a transparent electrode film.

To each of the first substrate and the second substrate was applied asolution of an alignment film material by spin casting, following bybaking at 200° C. Thereby, alignment films were formed.

The alignment films were each partially irradiated with polarized light(alignment treatment by light irradiation) such that the first alignmentfilm and the second alignment film can provide pre-tilt directions toliquid crystal molecules near them. The constituent molecules of thealignment films have photo-functional groups (photosensitive groups) ina side chain of a polymer. The alignment treatment causes dimerizationof the photo-functional groups such that they are dimerized and form acrosslinked structure.

Processes such as sealing and spacer scattering were performed, and thenthe first substrate and the second substrate were bonded to each otherin the substrate-bonding step. After this step, four domains providedwith different pre-tilt directions for the liquid crystal molecules canbe formed in each pixel.

Between the bonded first substrate and second substrate were injectedliquid crystal molecules having negative anisotropy of dielectricconstant. Polarizing plates were bonded to the substrates so that theazimuths of pre-tilt angles provided by the alignment films and thepolarization axes of the polarizing plates form four domain regions,namely a first alignment region provided with a pre-tilt direction at anazimuth of 225°, a second alignment region provided with a pre-tiltdirection at an azimuth of 135°, a third alignment region provided witha pre-tilt direction at an azimuth of 45°, and a fourth alignment regionprovided with a pre-tilt direction at an azimuth of 315°, with theazimuth in the transverse direction of pixels defined as 0°. Thereby,the liquid crystal display panel of Embodiment 1 was completed.Thereafter, a mounting step was performed to complete a liquid crystaldisplay device.

The alignment treatment in the method for manufacturing the liquidcrystal display panel of Embodiment 1 is described in detail below.

FIG. 39 is a schematic view of an UV exposure device in Embodiment 1.The UV light applied through a UV polarizer 1 is passed through a UVexposure mask 2 to be applied to a substrate 5. The substrate 5 may bethe first substrate or the second substrate. The UV light irradiationdirection (light irradiation direction) 3 indicates the UV lightirradiation direction in a plan view of the main surface of thesubstrate 5. The light irradiation direction can also be referred to asa light traveling direction when the light emitted by the light sourceis projected on the surface of the substrate 5. The substrate 5 is movedin a substrate-moving direction 4. In Embodiment 1, the UV lightirradiation direction 3 and the substrate-moving direction 4 areparallel to each other. Instead of the substrate, the light source maybe moved.

FIG. 40(a) is a schematic view showing first exposure in Embodiment 1.FIG. 41(a) is a schematic view showing second exposure in Embodiment 1.FIG. 40(b) and FIG. 41(b) are schematic plan views each showing thepolarization axis of the polarizer projected on a surface. In FIG. 39 toFIG. 41, the double-headed arrow on the UV polarizer 1 indicates apolarization axis 6 of the UV polarizer 1, and the white arrow on thesubstrate 5 indicates a pre-tilt direction 7 of the liquid crystalmolecules. The polarization axis 6 of the UV polarizer 1 and the UVlight irradiation direction 3 are substantially different from eachother, preferably forming an angle of approximately 45°. As shown inFIG. 40(b) and FIG. 41(b), the polarization axis 6 of the UV polarizer 1projected on the surface of the substrate 5 is preferably the same as apre-tilt azimuth 7. This configuration allows alignment of liquidcrystal molecules at a desired azimuth. Also, the polarization axis 6 ofthe UV polarizer 1 projected on the surface of the substrate 5 and thelight irradiation direction 6 may substantially form an angle of 45°.Thereby, alignment regions can be provided with a pre-tilt angle withhigher precision.

FIG. 42 is a schematic view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a substrate inthe liquid crystal display panel of Embodiment 1. For example, by asimple modification such as “polarization axis rotated by 45°” shown inFIG. 40, “polarization axis rotated by −45°” or “substrate rotated by90° before second exposure” shown in FIG. 41, a conventional exposuredevice can be modified into an exposure device suited to produce theliquid crystal display panel of the present invention.

Embodiment 2

FIG. 43 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Embodiment 2.

In Embodiment 2, linear electrode portions of the electrode arealternately connected to opposite sides of each of two linear electrodeportions constituting the cross-shaped electrode portion. Thisconfiguration can achieve the effect of the present invention andprevent accidental breaking of the cross-shaped electrode portion information of slits by patterning in the production step, enhancing theproduction yield.

The other configurations of the liquid crystal display panel ofEmbodiment 2 are similar to those of the liquid crystal display panel ofEmbodiment 1 described above.

Embodiment 3

FIG. 44 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Embodiment 3.

In Embodiment 3, the pixel electrodes each have a quadrangular portion,linear electrode portions extending from the quadrangular portion to besuperimposed on the boundaries between the four alignment regions, andlinear electrode portions extending from the quadrangular portion intothe respective four alignment regions. Such an electrode shape alsoenables achievement of the effect of the present invention.

The other configurations of the liquid crystal display panel ofEmbodiment 3 are similar to those of the liquid crystal display panel ofEmbodiment 1 described above.

Although the liquid crystal display panels of Embodiments 1 to 3described above include four alignment regions in each half pixel, theliquid crystal display panels may include four alignment regions in eachpixel. Such liquid crystal display panels can also achieve the effect ofthe present invention.

In Embodiments 1 to 3 described above, one of the TFT substrate and theCF substrate is exposed to light and the other is not exposed to lightin the first alignment region (1) and the second alignment region (2).

The past studies have revealed that such a region in which only one ofthe substrates is exposed to light can cause image sticking due toresidual direct current (DC). The method can be improved to avoid suchimage sticking, and a method solving this problem can be the followingEmbodiment 4.

Embodiment 4

FIG. 45 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, thirdexposure, fourth exposure, and all the exposure treatments of aphoto-alignment film of a TFT substrate, together with exposuredirections and scanning directions, in each half pixel in a liquidcrystal display panel of Embodiment 4. FIG. 46 is a conceptual viewshowing pre-tilt directions of liquid crystal molecules provided byfirst exposure, second exposure, third exposure, fourth exposure, andall the exposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Embodiment 4. FIG. 47 is aschematic plan view showing the relation between four domains, thealignment directions of liquid crystal molecules, and an electrodeprovided with slits in each half pixel in the liquid crystal displaypanel of Embodiment 4.

This method can eliminate regions provided with substantially nopre-tilt angle and can achieve the effect of the present invention whileavoiding image sticking. Yet, this method has a disadvantage that thenumber of exposure treatments increases from two as in Embodiments 1 to3 to four.

In the liquid crystal display panel of Embodiment 4, the photo-alignmentfilm of the TFT substrate and the photo-alignment film of the CFsubstrate provide different pre-tilt angles at azimuths perpendicular toeach other in each of the first alignment region (1), the secondalignment region (2), the third alignment region (3), and the fourthalignment region (4) (four quadrangular regions shown with the signs(1), (2), (3), and (4) in FIG. 47). These configurations are summarizedin the following Table 4. The exposure states corresponding to the“large”, “small”, and “none” under “pre-tilt” in the following Table 4are the same as those in the above Table 2.

TABLE 4 Pre-tilt Alignment achieved by Region TFT CF pre-tilt (UVexposure effect) (1) Large Small Tilt near TFT is dominant (slightlytwisted alignment) (2) Small Large Tilt near CF is dominant (slightlytwisted alignment) (3) Large Small Tilt near TFT is dominant (slightlytwisted alignment) (4) Small Large Tilt near CF is dominant (slightlytwisted alignment)

Comparative Example 1

FIG. 48 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and aplanar electrode in each half pixel in a liquid crystal display panel ofComparative Example 1. FIG. 49 is a conceptual view showing pre-tiltdirections of liquid crystal molecules provided by first exposure,second exposure, and both of the exposure treatments of aphoto-alignment film of a TFT substrate in each half pixel in the liquidcrystal display panel of Comparative Example 1. FIG. 50 is a conceptualview showing pre-tilt directions of liquid crystal molecules provided byfirst exposure, second exposure, and both of the exposure treatments ofa photo-alignment film of a CF substrate in each half pixel in theliquid crystal display panel of Comparative Example 1. The liquidcrystal display panel of Comparative Example 1 causes fylfot dark linesas shown in FIG. 48.

FIG. 51 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and aplanar electrode in each half pixel of 82 μm×245 μm pixels included inthe liquid crystal display panel of Comparative Example 1. FIG. 52 is asimulation result corresponding to FIG. 51. As the definition of aliquid crystal display panel increases and the pixel size decreases, theproportion of fylfot dark lines, formed by irregular alignment regionsgenerated in the pixel edge portions indicated by dotted lines and darklines generated in a crossed shape at the center of each pixel,increases in a pixel. This tends to cause unstable alignment anddecreases the transmittance and the response performance. Here,irregular alignment regions generated in the pixel edge portionssurrounded by dashed lines are due to a twist angle greater than 90°formed by the long-axis directions of liquid crystal molecules affectedby oblique electric fields generated by the edge portions of the slitelectrodes (liquid crystal molecules LC1 on the outline of thequadrangular half pixel) and the long-axis directions of liquid crystalmolecules LC2 in the domain.

FIG. 53 is a schematic plan view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate and a pre-tilt direction ofliquid crystal molecules near the CF substrate, in each half pixel inthe liquid crystal display panel of Comparative Example 1. FIG. 54 is aschematic plan view showing a planar electrode in each half pixel in theliquid crystal display panel of Comparative Example 1.

The liquid crystal display panel of Comparative Example 1 can achievethe alignment shown in FIG. 48 by the four-division alignment (pre-tilt)structure of liquid crystal molecules shown in FIG. 53 and the alignmentachieved by the electric fields generated by the planar electrode shownin FIG. 54 in combination.

(Mark Left by Pushing with Finger on 4D-RTN Alignment Liquid CrystalDisplay Panel)

FIG. 55 is a conceptual view showing a pre-tilt direction of liquidcrystal molecules near the TFT substrate, a pre-tilt direction of liquidcrystal molecules near the CF substrate, and liquid crystal layeralignment, in each half pixel in a 4D-RTN alignment liquid crystaldisplay panel. The liquid crystal display panel shown in FIG. 55 issimilar to that of Comparative Example 1, except that the slit electrodeshown in FIG. 55 is used instead of the planar electrode as theelectrode. This liquid crystal display panel corresponds to a modifiedexample of Comparative Example 1. FIG. 56 shows alignment of liquidcrystal molecules achieved by the pre-tilt provided by the TFT substrateof the liquid crystal display panel shown in FIG. 55. FIG. 57 showsalignment of liquid crystal molecules achieved by electric fieldsgenerated by a slit electrode of the TFT substrate in the liquid crystaldisplay panel shown in FIG. 55. FIG. 56 and FIG. 57 are enlarged viewsof the portion surrounded by a dashed line in FIG. 55, showing thealignment of the liquid crystal molecules near the slit electrode andthe TFT substrate.

As in the case of a 4D-ECB alignment liquid crystal display panel, thealignment of liquid crystal molecules near the TFT substrate (thoseadjacent to the TFT substrate) including slit electrodes is setdepending on the balance between (1) alignment achieved by the pre-tiltand (2) alignment achieved by electric fields generated by the slitelectrodes. In the normal state (when the finger is removed), thealignment (1) achieved by the pre-tilt is dominant, whereas upon pushingwith a finger, the gap between the TFT substrate and the CF substratebecomes narrow and thus the alignment (2) achieved by electric fieldsgenerated by the slit electrode is dominant.

FIG. 58 shows alignment of liquid crystal molecules near the TFTsubstrate and in the liquid crystal layer upon pushing with a finger andupon removal of the finger in the liquid crystal display panel shown inFIG. 55. In FIG. 58, the “provided” state for the “slit” means that theliquid crystal display panel includes the slit electrode shown in FIG.55. The “not provided” state for the “slit” means that the liquidcrystal display panel of Comparative Example 1 includes no slitelectrode but includes a planar electrode (the liquid crystal displaypanel different from the liquid crystal display panel shown in FIG. 55only in terms of including a planar electrode instead of the slitelectrode). The “alignment near TFT substrate” or “TFT alignment” meansthe alignment of liquid crystal molecules near the TFT substrate in theliquid crystal layer. The “liquid crystal layer alignment” means thealignment of liquid crystal molecules in the liquid crystal layer or thealignment of liquid crystal molecules in the center portion, which isother than the portion near the TFT substrate and the portion near theCF substrate, in the liquid crystal layer. The “CF alignment” means thealignment of liquid crystal molecules near the CF substrate. In the4D-RTN alignment liquid crystal display panel including the slitelectrode shown in FIG. 55, the liquid crystal layer is provided withtwist alignment and liquid crystal molecules in the portion indicated bythe letter “A” and liquid crystal molecules in the portion indicated bythe letter “B” in the center portion of the liquid crystal layer areconsidered to be shifted from Alignment a to Alignment b withoutstopping when the states shift from pushing with a finger to removal ofthe finger. Liquid crystal molecules in the portion indicated by theletter “C” in the center portion of the liquid crystal layer, however,become parallel to the pre-tilt direction of the liquid crystalmolecules near the CF substrate (Alignment c) in the course of the shiftfrom Alignment a to Alignment b. This means that the liquid crystalmolecules are trapped in this stable state without a twist and fail tobe shifted to Alignment b. This phenomenon is presumed to cause darklines and a mark left by pushing with a finger. In the liquid crystaldisplay panel including a planar electrode instead of a slit electrode,the alignment of liquid crystal molecules in any of the portions doesnot change between pushing with a finger and removal of the finger, andthus no mark is left by pushing with a finger.

FIG. 59 is a schematic view of an exposure device in ComparativeExample 1. FIG. 60 is a schematic view showing first exposure inComparative Example 1. FIG. 61 is a schematic view showing secondexposure in Comparative Example 1. FIG. 62 is a schematic view showingpre-tilt directions of liquid crystal molecules provided by firstexposure, second exposure, and both of the exposure treatments of aphoto-alignment film of a substrate in the liquid crystal display panelof Comparative Example 1. These exposure treatments can be performedusing a conventional exposure device.

(Reason for Difficulty in Scanning in Direction Perpendicular toExposure Direction)

(1) In the Case where Exposure Direction and Scanning Direction areParallel

FIG. 63 is a schematic plan view whose left part shows exposure of aphoto-alignment film in the case of parallel exposure direction andscanning direction viewed from directly above the photo-alignment filmand whose right part is a graph showing incident angle distribution oflight from a light source along the y1-y2 axis in the left part. FIG. 64is a perspective view of exposure of a photo-alignment film in the caseof parallel exposure direction and scanning direction.

As shown in FIG. 64, in an ultraviolet light (UV light) irradiation areaby one light source, the incident angle is almost the same at anyposition (θ_(A)≈θ_(B)). Hence, the pre-tilt angle of the liquid crystalmolecules LC does not vary, and thus the liquid crystal display deviceincluding the photo-alignment films obtained in this manner can exhibitexcellent display quality.

(2) In the Case where Exposure Direction and Scanning Direction arePerpendicular

FIG. 65 is a schematic plan view whose left part shows exposure of aphoto-alignment film in the case of perpendicular exposure direction andscanning direction viewed from directly above the photo-alignment filmand whose right part is a graph showing incident angle distribution oflight from a light source along the y1-y2 axis in the left part. FIG. 66is a perspective view of exposure of a photo-alignment film in the caseof perpendicular exposure direction and scanning direction.

As shown in FIG. 66, in a UV light irradiation area by one light source,the incident angle varies in the irradiation area (θ_(A)≠θ_(B)). Morespecifically, the incident angle is smaller at a position farther fromthe light source, showing incident angle distribution in the Ydirection. This increases variation of the pre-tilt angle of liquidcrystal molecules LC, and thus the resulting liquid crystal displaydevice including the photo-alignment films obtained in this mannerexhibits poor display quality.

Comparative Example 2

FIG. 67 is a schematic plan view showing the relation between fourdomains, the alignment directions of liquid crystal molecules, and anelectrode provided with slits in each half pixel in a liquid crystaldisplay panel of Comparative Example 2. FIG. 67 shows the above relationin the ON state (in white display). FIG. 68 is a schematic plan viewshowing pre-tilt directions of liquid crystal molecules provided byfirst exposure, second exposure, and both of the exposure treatments ofa photo-alignment film of a TFT substrate in each half pixel in theliquid crystal display panel of Comparative Example 2. FIG. 69 is aschematic plan view showing pre-tilt directions of liquid crystalmolecules provided by first exposure, second exposure, and both of theexposure treatments of a photo-alignment film of a CF substrate in eachhalf pixel in the liquid crystal display panel of Comparative Example 2.

In the liquid crystal display panel of Comparative Example 2, the liquidcrystal layer is provided with twist alignment, and the direction inwhich liquid crystal molecules are rotated for alignment by electricfields generated by slit electrodes is different from the pre-tiltdirection provided by the photo-alignment film(s) of the TFT substrateand/or the CF substrate. Hence, a mark left by pushing with a finger wasnot removed as in the case of the modified example of ComparativeExample 1.

FIG. 70 is a conceptual view showing pre-tilt directions of liquidcrystal molecules provided by first exposure, second exposure, and bothof the exposure treatments of a photo-alignment film of a TFT substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Comparative Example 2. FIG.71 is a conceptual view showing pre-tilt directions of liquid crystalmolecules provided by first exposure, second exposure, and both of theexposure treatments of a photo-alignment film of a CF substrate,together with exposure directions and scanning directions, in each halfpixel in the liquid crystal display panel of Comparative Example 2.

In the liquid crystal display panel of Comparative Example 2, thescanning direction and the exposure direction are perpendicular to eachother, so that scanning with a conventional exposure device is difficultand therefore production is difficult.

Examples of the liquid crystal display device including the liquidcrystal display panel of the present invention include on-board devicessuch as automotive navigation systems, electronic book readers, digitalphoto frames, industrial equipment, televisions, personal computers,smartphones, and tablet PCs. The present invention is preferably appliedto devices that can be used both at high temperatures and lowtemperatures, including on-board devices such as automotive navigationsystems.

By observation of the TFT substrate with a microscope such as a scanningelectric microscope (SEM), the electrode structure, for example, of theliquid crystal display panel of the present invention can be determined.

REFERENCE SIGNS LIST

-   LC: liquid crystal molecule-   A, B, C: position (of liquid crystal molecules)-   a, b, c: alignment-   1, 11: UV polarizer-   2, 12: UV exposure mask-   3, 13: UV light irradiation direction-   4, 14: moving direction of substrate-   5, 15: substrate-   6: polarization axis-   7: pre-tilt azimuth-   111, 211: first polarizing plate-   111 a, 211 a: polarization axis-   113, 213: substrate including TFT-   115, 125, 215, 225: ITO-   117, 127, 217, 227: photo-alignment film-   121, 221: second polarizing plate-   121 a, 221 a: polarization axis-   123, 223: substrate including CF

The invention claimed is:
 1. A liquid crystal display panel includingmultiple pixels arranged in a matrix, comprising in the given order: afirst polarizing plate; a first substrate including pixel electrodeseach provided with a slit; a first alignment film; a liquid crystallayer containing liquid crystal molecules having negative anisotropy ofdielectric constant; a second alignment film; a second substrateincluding a counter electrode; and a second polarizing plate, the firstpolarizing plate and the second polarizing plate being arranged suchthat their polarization axes are perpendicular to each other, with anazimuth in a transverse direction of each pixel defined as 0°, the pixelelectrode in each of the pixels including a first linear electrode groupextending parallel to an azimuth of approximately 45°, a second linearelectrode group extending parallel to an azimuth of approximately 135°,a third linear electrode group extending parallel to an azimuth ofapproximately 225°, and a fourth linear electrode group extendingparallel to an azimuth of approximately 315°, the first alignment filmand the second alignment film each aligning the liquid crystal moleculesin a direction approximately perpendicular to a film surface with novoltage applied to the liquid crystal layer while providing a pre-tiltangle to the liquid crystal molecules in at least one region, the firstalignment film and the second alignment film each including a firstalignment region superimposed on the first linear electrode group, asecond alignment region superimposed on the second linear electrodegroup, a third alignment region superimposed on the third linearelectrode group, and a fourth alignment region superimposed on thefourth linear electrode group, the first alignment regions, the secondalignment regions, the third alignment regions and the fourth alignmentregions are arranged sequentially counterclockwise in a matrix shape oftwo lines and two rows, one of the first alignment film and the secondalignment film including the first alignment region provided with apre-tilt angle at an azimuth of approximately 225°, the second alignmentregion provided with substantially no pre-tilt angle, the thirdalignment region provided with a pre-tilt angle at an azimuth ofapproximately 45°, and the fourth alignment region provided with apre-tilt angle at an azimuth approximately perpendicular to the fourthlinear electrode group, the other of the first alignment film and thesecond alignment film including the first alignment region provided withsubstantially no pre-tilt angle, the second alignment region providedwith a pre-tilt angle at an azimuth of approximately 135°, the thirdalignment region provided with a pre-tilt angle at an azimuthapproximately perpendicular to the third linear electrode group, and thefourth alignment region provided with a pre-tilt angle at an azimuth ofapproximately 315°, the azimuth of the third alignment region of thefirst alignment film being parallel or anti-parallel to the azimuth ofthe fourth alignment region of the first alignment film and, the azimuthof the third alignment region of the second alignment film beingparallel or anti-parallel to the azimuth of the fourth alignment regionof the second alignment film.
 2. The liquid crystal display panelaccording to claim 1, wherein the alignment films are photo-alignmentfilms providing a pre-tilt angle to the liquid crystal molecules in aregion subjected to photo-alignment treatment.
 3. A method formanufacturing the liquid crystal display panel according to claim 2,comprising a photo-alignment treatment step of irradiating a firstsubstrate provided with a first alignment film on a surface and a secondsubstrate provided with a second alignment film on a surface with lightemitted by a light source through a polarizer, wherein thephoto-alignment treatment step is performed while the first substrate orthe second substrate is moved or the light source is moved relative tothe first substrate or the second substrate, the light irradiationdirection for the first substrate or the second substrate is parallel tothe moving direction of the first substrate or the second substrate orthe moving direction of the light source, and a polarization axis of thepolarizer and the light irradiation direction are different from eachother.
 4. The method according to claim 3, wherein the polarization axisof the polarizer and the light irradiation direction form an angle ofapproximately 45°.
 5. The liquid crystal display panel according toclaim 1, wherein each pixel electrode includes a cross-shaped electrodeportion superimposed on boundaries between the first alignment region,the second alignment region, the third alignment region, and the fourthalignment region in a plan view, and the first linear electrode group,the second linear electrode group, the third linear electrode group, andthe fourth linear electrode group which extend from the cross-shapedelectrode portion.
 6. The liquid crystal display panel according toclaim 5, wherein the first linear electrode group, the second linearelectrode group, the third linear electrode group, and the fourth linearelectrode group are line-symmetric about at least one of two linearportions constituting the cross-shaped electrode portion.
 7. The liquidcrystal display panel according to claim 5, wherein the first linearelectrode group, the second linear electrode group, the third linearelectrode group, and the fourth linear electrode group are alternatelyconnected to opposite sides of at least one of two linear portionsconstituting the cross-shaped electrode portion.
 8. The liquid crystaldisplay panel according to claim 1, wherein each pixel electrodeincludes a quadrangular portion, linear electrode portions extendingfrom the quadrangular portion to be superimposed on boundaries betweenthe first alignment region, the second alignment region, the thirdalignment region, and the fourth alignment region in a plan view, andthe first linear electrode group, the second linear electrode group, thethird linear electrode group, and the fourth linear electrode groupwhich extend from the quadrangular portion and the linear electrodeportions.
 9. A method for manufacturing a liquid crystal display panel,the liquid crystal display panel including multiple pixels arranged in amatrix, the liquid crystal display panel comprising in the given order:a first polarizing plate; a first substrate including pixel electrodeseach provided with a slit; a first alignment film; a liquid crystallayer containing liquid crystal molecules having negative anisotropy ofdielectric constant; a second alignment film; a second substrateincluding a counter electrode; and a second polarizing plate, the firstpolarizing plate and the second polarizing plate being arranged suchthat their polarization axes are perpendicular to each other, with anazimuth in a transverse direction of each pixel defined as 0°, the pixelelectrode in each of the pixels including a first linear electrode groupextending parallel to an azimuth of approximately 45°, a second linearelectrode group extending parallel to an azimuth of approximately 135°,a third linear electrode group extending parallel to an azimuth ofapproximately 225°, and a fourth linear electrode group extendingparallel to an azimuth of approximately 315°, the first alignment filmand the second alignment film each aligning the liquid crystal moleculesin a direction approximately perpendicular to a film surface with novoltage applied to the liquid crystal layer while providing a pre-tiltangle to the liquid crystal molecules in at least one region, the firstalignment film and the second alignment film each including a firstalignment region superimposed on the first linear electrode group, asecond alignment region superimposed on the second linear electrodegroup, a third alignment region superimposed on the third linearelectrode group, and a fourth alignment region superimposed on thefourth linear electrode group, the first alignment regions, the secondalignment regions, the third alignment regions and the fourth alignmentregions are arranged sequentially counterclockwise in a matrix shape oftwo lines and two rows, one of the first alignment film and the secondalignment film including the first alignment region provided with apre-tilt angle at an azimuth of approximately 225°, the second alignmentregion provided with substantially no pre-tilt angle, the thirdalignment region provided with a pre-tilt angle at an azimuth ofapproximately 45°, and the fourth alignment region provided with apre-tilt angle at an azimuth approximately perpendicular to the fourthlinear electrode group, the other of the first alignment film and thesecond alignment film including the first alignment region provided withsubstantially no pre-tilt angle, the second alignment region providedwith a pre-tilt angle at an azimuth of approximately 135°, the thirdalignment region provided with a pre-tilt angle at an azimuthapproximately perpendicular to the third linear electrode group, and thefourth alignment region provided with a pre-tilt angle at an azimuth ofapproximately 315°, the azimuth of the third alignment region of thefirst alignment film being parallel or anti-parallel to the azimuth ofthe fourth alignment region of the first alignment film, the azimuth ofthe third alignment region of the second alignment film being parallelor anti-parallel to the azimuth of the fourth alignment region of thesecond alignment film, and the alignment films are photo-alignment filmsproviding a pre-tilt angle to the liquid crystal molecules in a regionsubjected to photo-alignment treatment, the method comprising aphoto-alignment treatment step of irradiating the first substrateprovided with the first alignment film on a surface and the secondsubstrate provided with the second alignment film on a surface withlight emitted by a light source through a polarizer, wherein thephoto-alignment treatment step is performed while the first substrate orthe second substrate is moved or the light source is moved relative tothe first substrate or the second substrate, the light irradiationdirection for the first substrate or the second substrate is parallel tothe moving direction of the first substrate or the second substrate orthe moving direction of the light source, and a polarization axis of thepolarizer projected on a surface of the first substrate or a surface ofthe second substrate and the light irradiation direction form an angleof approximately 45°.
 10. The method for manufacturing the liquidcrystal display panel according to claim 9, wherein the photo-alignmenttreatment step includes a first exposure of irradiating a first regionof the first alignment film or the second alignment with light, and asecond exposure of irradiating the first region with light.
 11. Themethod for manufacturing the liquid crystal display panel according toclaim 10, wherein light irradiation directions in the first exposure andthe second exposure are different from each other.